eDNA Collection

Terrestrial eDNA sampling is a novel and minimally invasive way to detect bee species by analyzing the DNA they leave behind on flowering plants when collecting pollen and nectar. In an effort to further the search for the Franklin's Bumble Bee, eDNA collection has begun in historic Franklin's locations. In 2024, a pilot study was conducted in the Mt. Ashland area where three plots were surveyed (one in July and two in August). We repeated the eDNA collection process at two of the three sites in July of 2025. While the flower samples from both years have not been processed yet, we have data on the bumble bee species present in each plot, the number of each species present in each plot, the species of flowering plant in each plot, the magnitude of inflorescences of each flowering plant species, and which bee species were found on which flowering plant.

This survey was designed and conducted by David S. Pilliod, Jeffery G. Everett, and Michaela R. Grossklaus.

2024 Pilot Study

This interaction web displays the relationships between bumblebee species and plant species observed in 2024 across the three sampled sites. Before a flower head was sampled for eDNA analysis, researchers recorded which species of bumblebee was visiting the plant. At each plot, five flowering plants were sampled. Ideally, five distinct species in full bloom were selected; however, when fewer than five suitable plant species were available, some species were resampled.

This web allows us to begin identifying which Bombus species exhibit more generalist foraging strategy and which plant species are favored by Bombus populations in the sites.

Vancouver Bumblebee B. vancouverensis

In 2024, B. vancouverensis visited the highest amount of flowering plant species within the surveyed areas (11/13 sampled plants).

Yellow-faced Bumblebee B. vosnesenskii

In 2024, B. vosnesenskii visited the second highest amount of flowering plant species within the sruveyed areas (10/13 sampled plants).

Nettleleaf giant hyssop Agastache urticifolia

Nettleleaf giant hyssop was visited by the highest amount of Bombus species (6 species).

Community Composition Within Plots

This figure displays the percent relative abundance of bumblebee species in 2024 and 2025. In both years, researchers conducted a visual encounter survey immediately following eDNA sampling . At each plot, surveys were conducted for a total of 45 person-minutes (i.e., 45 minutes divided by the number of surveyors). Surveyors tallied all bumble bee species encountered, and these counts were combined across surveyors and plots at the end of each day. These totals were then used to calculate the relative abundance of each species. Note that the 2024 data include observations from three plots, while the 2025 data include two plots within the Mt. Ashland area.

eDNA survey

The "total bee counts" page was used to generate the community composition by year with a total of 478 bumble bees observed across the three sites in 2024 and a total of 356 bumble bees observed across the two sites in 2025. The "2024 bee/plant web" page was used to generate the bee-plant interaction web. The following two pages show the breakdown of total species counts, though we have more specific data for 2025, noting caste and a breakdown across the two sites.

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